Within the supermarket and merchandising industries, many different styles of check-out counter systems are in use. With increasing labor costs and improved data systems, the pressure for productivity at the check-out location of these industries has increased dramatically.
In the late 1970s, mechanical cash registers were being replaced by integrated points of sales terminals, leading to different work procedures, increased work rates, and reduced labor requirements. Significant gains in productivity were realized. The resulting check-out counter systems have been typically designed to move products and to provide the customer with needed services. However, little attention has been given to the cashiers who have operated these check-out counter systems. The human doing the job is required to adapt to the system. Apparent incompatibilities between the cashier, the work procedures and the check-out counter design have led to increased health complaints and workers' compensation claims and disability lawsuits. The major time loss claim is due to over exertion leading to strains and sprains of the lower back and upper extremities. The real tragedy is that many workers in this environment are suffering from permanently disabling injuries.
It is only in recent years that certain of these injuries have been identified as work related. Biomechanical studies indicate that the lower back is vulnerable to continual over stress damage during even moderate load handling, but that the symptoms may not manifest themselves until later in life. Carpal tunnel syndrome--a present day "buzz word" in this industry-- and related injuries such as tendinitis, tenosynovitis and De Quervain's Disease are apparently caused by injuries which build up gradually over time before symptoms begin to appear. Tasks which are highly repetitive in nature dramatically increase the risk of injury. Fatigue also appears to be one of the underlying causes of many of the symptoms experienced by cashiers at check-out counter systems. There are many human factors affecting the task performed at check-out counter systems, but there is little "hard" data to work with. It is known that certain repetitive tasks have the potential to cause cumulative trauma disorders, but critical levels of repetitiveness have not been determined, and critical force levels are not known. Although some individuals are far more susceptible to repetitive injuries than others, there is no reliable method of determining who is the most vulnerable.
During the last few years, there has been increasing interest throughout the supermarket and merchandising industries in the application of ergonomic principles to the check-out counter system. Retail clerks' unions are becoming active in this area and OSHA has brought the supermarket front-end under scrutiny. However, the supermarket check-out counter systems present ergonomic problems which do not lend themselves to easy solutions.
Nearly all check-out counter systems in the United States and Canada are designed so that cashiers must work in a standing posture. When seating is not available at the check-out counter systems, cashiers report discomfort and pain in the legs, apparently caused by prolonged standing. In contrast, most check-out counter systems in Europe and some other parts of the world are designed so that the cashiers work in a seated position. Studies have shown that prolonged sitting is associated with increased rates of low-back pain, probably caused by rotation of the pelvis.
Working continuously in either a standing or seated position has disadvantages. When working in a standing posture, muscles in the legs, feet and lower back must work constantly to maintain this posture. Heavy loads are placed on the feet. As each major muscle group remains tensed, circulation through these muscles is reduced, nutrient flow to the muscles is restricted, and the chemical products of fatigue build up in the tissues. On the other hand, when working continuously in a seated position, continuous tensing of specific muscle groups occurs. Circulation to the legs is further restricted by pressure from the chair seat. When assuming a seated posture, the lower lumbar curve of the back becomes nearly straight and this rotates all of the vertebra in this section of the back out of their neutral position into a position in which the torso loads are concentrated on the front of each vertebra and disc. The net result is a reduction of the lower back strength of about 30%. When working in a seated position it is physically difficult to handle bulky items and it is impossible to use the legs to assist in lifting heavy items.
In addition, there are two basic types of check-out counter systems, i.e. customer unload and cashier unload. With customer unload check-out counter systems, the customers places his order on the top of the check-out counter so that the cashier can record the price of each item. The top of the check-out is usually provided with a conveyor belt to transport the order to the cashier. The top surface of the customer unload check-out is typically 35 to 38 inches above the surface on which the cashier is standing. With cashier unload check-out counter systems, the cashier removes the customer's order from the shopping cart and records the price of each item. The top surface of the cashier unload check-out is typically 29 to 32 inches above the surface on which the cashier is standing.
With both systems, after the price of each item has been recorded, the customer's order is placed in boxes, paper bags or plastic bags by the cashier or by a professional bagger. The bagging operation is performed on the check-out surface, on a special bagging shelf or platform that is part of the check-out counter system, or on bagging racks which can be placed on either of the above mentioned surfaces or suspended from the end of the check-out counter system. In all cases the bagging surface is fixed at one height above the floor.
In that regard, anthropometric data reveals that the 5th percentile female is just under 5 feet tall and that the 95th percent male is over 6 feet 2 inches tall. When the surface of a work place is at a correct height, the operator is able to work with the upper arms hanging relaxed and the wrist 1 to 4 inches lower than the elbow. It has been found by applying anthropometric data to these requirements that the working surface for a 5 foot tall person should be 34 to 36 inches high and the working surface for a 6 foot 2 inch person should be 41 to 43 inches high. To applicant's knowledge, no check-out counter systems have heretofore recognized or made any allowances for these requirements and differences in human heights of the operator.
All check-out counter systems must have a keyboard to enter price data. These keyboards have been placed in many different locations in check-out counter systems. In some check-out counter systems, the keyboards have been made adjustable up and down relative to the check-out counter and sometimes the angle can be adjusted. However, to applicant's knowledge no one has ever taken into consideration the fact that many people are left-handed. The best location for a keyboard from an ergonomic viewpoint is directly in front of the cashier, at a height and angle that allows the cashier to operate the keyboard with his upper arm hanging in a relaxed position and the wrist within 15 degrees of a neutral (straight) posture. Keyboards mounted in this way are typically placed directly in front of the cashier's right shoulder, since the majority of our population are right-handed. For a left-handed operator to use this keyboard, the left arm must be extended across in front of the body and the left wrist must be bent back to the left at an uncomfortable angle.
It has been found that for maximum productivity when business is light, the most cost-effective and productive system of processing goods at the check-out counter is one in which the cashier grasps each item, records its price (either manually with the keyboard or with the use of a laser scanner), then places it directly in a bag for the customer. This is referred to as "direct bagging". It has the advantage of using only one worker and of handling each item only once. On the other hand, when business becomes heavy, it is advantageous to be able to add manpower, such as a bagger, to the process in order to speed customers through the check-out as fast as possible. Prior check-out counter systems have not been specifically designed to best accommodate both of these procedures.